1. Related Technical Fields
Related technical fields include navigation systems, particularly for distributing traffic congestion information from an information distribution center to a navigation apparatus.
2. Description of the Related Art
In resent years, a navigation apparatus for enabling a driver to easily navigate a vehicle to a desired destination has become very popular. The navigation apparatus detects a current position of the vehicle, for example, by GPS, obtains map data corresponding to the current position through a data storage medium, such as a DVD-ROM or an HDD, or a network, and displays the map on an LCD monitor. The navigation apparatus reads out map data including a current position of the vehicle from the data storage medium and displays the map surrounding the current vehicle position on a display device on the basis of the map data. The navigation apparatus indicates the position of the vehicle on the map using a position indicator. The map may be scrolled according to the traveling direction of the vehicle or the vehicle position indicator may be relocated over the fixed map, so that the driver may check where the vehicle is currently traveling at a glance.
Such navigation system may also distribute traffic congestion information from an information distribution center to a navigation apparatus. For example, Japanese Unexamined Patent Application Publication No. 2004-20288 (paragraph [0011] to paragraph [0039], FIGS. 1 to 6) discloses a navigation apparatus that calculates a time required to pass through a road section when traveling along the road section and reports the required travel time to an information distribution center. The navigation apparatus requests a latest required travel time for a road section, on which the vehicle will be traveling, from the information distribution center, and predicts an arrival time to a destination on the basis of the information received from the information distribution center. The information distribution center receives required section travel time information reported from the vehicle and stores required travel times for road sections on a road. The information distribution center gathers statistics about required section travel time information from vehicles and updates statistical information in the required section travel time database. The information distribution center estimates a required section travel time corresponding to the road section requested by the vehicle and then transfers the estimated required section travel time information to the vehicle.
Thus, in the navigation system of Japanese Unexamined Patent Application Publication No. 2004-20288, the information distribution center stores the latest required travel times of road sections reported from vehicles in a database. When the driver of one of the vehicles wants to know an arrival time to a destination, the navigation system in the vehicle requests and obtains the latest travel time of a road section on which the vehicle is currently traveling to the information distribution center and predicts the arrival time to the destination on the basis of the latest travel time for the road section. As a result, the navigation system may predict the arrival time to the destination according to the traffic congestion situation at a given time even if a traffic analysis apparatus is not set on the road section.